Cardiac aetiology accounts for approximately 20% of strokes in young adults. Although atrial fibrillation is a leading cause of stroke in the general population, it is uncommon in young adults. In such patients, more diverse causes of ischaemic stroke are observed, including valvular heart diseases, infective endocarditis, Libman–Sacks endocarditis, dilated cardiomyopathies, congenital heart diseases, myocardial infarction, and intracardiac tumours. Patent foramen ovale is commonly observed in young adults with ischaemic stroke, but this association may be incidental in a sizeable proportion of patients. Young adults who are the most likely to have a stroke-related patent foramen ovale are also those with the lowest recurrence risk.